def mix_ciphers(ciphers_for_mixing, nr_rounds=MIN_MIX_ROUNDS,
teller=_teller, nr_parallel=0):
p = ciphers_for_mixing['modulus']
g = ciphers_for_mixing['generator']
q = ciphers_for_mixing['order']
y = ciphers_for_mixing['public']
original_ciphers = ciphers_for_mixing['mixed_ciphers']
nr_ciphers = len(original_ciphers)
teller.task('Mixing %d ciphers for %d rounds' % (nr_ciphers, nr_rounds))
cipher_mix = {'modulus': p, 'generator': g, 'order': q, 'public': y}
cipher_mix['original_ciphers'] = original_ciphers
with teller.task('Producing final mixed ciphers', total=nr_ciphers):
shuffled = shuffle_ciphers(p, g, q, y, original_ciphers, teller=teller)
mixed_ciphers, mixed_offsets, mixed_randoms = shuffled
cipher_mix['mixed_ciphers'] = mixed_ciphers
total = nr_ciphers * nr_rounds
with teller.task('Producing ciphers for proof', total=total):
if nr_parallel > 0:
pool = Pool(nr_parallel, Random.atfork)
data = [
(p, g, q, y, original_ciphers)
for _ in range(nr_rounds)
]
collections = []
for r in pool.imap(_shuffle_ciphers, data):
teller.advance()
collections.append(r)
pool.close()
pool.join()
else:
collections = [shuffle_ciphers(p, g, q, y,
original_ciphers, teller=teller)
for _ in range(nr_rounds)]
unzipped = [list(x) for x in zip(*collections)]
cipher_collections, offset_collections, random_collections = unzipped
cipher_mix['cipher_collections'] = cipher_collections
cipher_mix['random_collections'] = random_collections
cipher_mix['offset_collections'] = offset_collections
with teller.task('Producing cryptographic hash challenge'):
challenge = compute_mix_challenge(cipher_mix)
cipher_mix['challenge'] = challenge
bits = bit_iterator(int(challenge, 16))
with teller.task('Answering according to challenge', total=nr_rounds):
for i, bit in zip(range(nr_rounds), bits):
offsets = offset_collections[i]
randoms = random_collections[i]
if bit == 0:
# Nothing to do, we just publish our offsets and randoms
pass
elif bit == 1:
# The image is given. We now have to prove we know
# both this image's and mixed_ciphers' offsets/randoms
# by providing new offsets/randoms so one can reencode
# this image to end up with mixed_ciphers.
# original_ciphers -> image
# original_ciphers -> mixed_ciphers
# Provide image -> mixed_ciphers
new_offsets = list([None]) * nr_ciphers
new_randoms = list([None]) * nr_ciphers
for j in range(nr_ciphers):
cipher_random = randoms[j]
cipher_offset = offsets[j]
mixed_random = mixed_randoms[j]
mixed_offset = mixed_offsets[j]
new_offsets[cipher_offset] = mixed_offset
new_random = (mixed_random - cipher_random) % q
new_randoms[cipher_offset] = new_random
offset_collections[i] = new_offsets
random_collections[i] = new_randoms
del offsets, randoms
else:
m = "This should be impossible. Something is broken."
raise AssertionError(m)
teller.advance()
teller.finish('Mixing')
return cipher_mix
def verify_cipher_mix(cipher_mix, teller=_teller, nr_parallel=0):
try:
p = cipher_mix['modulus']
g = cipher_mix['generator']
q = cipher_mix['order']
y = cipher_mix['public']
original_ciphers = cipher_mix['original_ciphers']
mixed_ciphers = cipher_mix['mixed_ciphers']
challenge = cipher_mix['challenge']
cipher_collections = cipher_mix['cipher_collections']
offset_collections = cipher_mix['offset_collections']
random_collections = cipher_mix['random_collections']
except KeyError as e:
m = "Invalid cipher mix format"
raise ZeusError(m, e)
if compute_mix_challenge(cipher_mix) != challenge:
m = "Invalid challenge"
raise ZeusError(m)
nr_ciphers = len(original_ciphers)
nr_rounds = len(cipher_collections)
teller.task('Verifying mixing of %d ciphers for %d rounds'
% (nr_ciphers, nr_rounds))
if (len(offset_collections) != nr_rounds or
len(random_collections) != nr_rounds):
m = "Invalid cipher mix format: collections not of the same size!"
raise ZeusError(m)
#if not validate_cryptosystem(p, g, q, teller):
# m = "Invalid cryptosystem"
# raise AssertionError(m)
total = nr_rounds * nr_ciphers
with teller.task('Verifying ciphers', total=total):
data = []
for i, bit in zip(range(nr_rounds), bit_iterator(int(challenge, 16))):
ciphers = cipher_collections[i]
randoms = random_collections[i]
offsets = offset_collections[i]
data.append((p, g, q, y,
i, bit, original_ciphers,
mixed_ciphers, ciphers,
randoms, offsets))
if nr_parallel <= 0:
for args in data:
verify_mix_round(*args, teller=teller)
else:
pool = Pool(nr_parallel, Random.atfork)
try:
for count in pool.imap(_verify_mix_round, data):
teller.advance(count)
finally:
pool.terminate()
pool.join()
teller.finish('Verifying mixing')
return 1